The present invention is directed to the art of improving the surface morphology of silicone rubber catheters, particularly urethral catheters.
In general, catheters may be described as tubular, flexible, surgical instruments for withdrawing fluids from or introducing fluids into a body cavity. Although catheters are employed for various purposes, the most common usage and the one generally thought of when one mentions catheterization is the catheter introduced into the bladder through the urethra for withdrawal of urine.
While some catheters are employed intermittently, more typically they are indwelling, i.e. retained in the body cavity for extended periods of time. As examples of indwelling catheters, mention may be made of urethral catheters for withdrawal of urine, e.g. Foley catheters, which are retained in the bladder by a balloon which may be inflated with air or liquid; and winged catheters which are provided with two projections at the end inserted in order to retain it in the bladder.
Typically, catheters are made of silicone rubber, latex or some suitable medical grade polymer such as polyvinyl chloride.
Particularly with the use of indwelling catheters such as urethral and venous catheters, it is well recognized that they are often a prime avenue for the introduction of pathogenic organisms. This is perhaps more prevalent with indwelling catheters such as the commonly employed Foley catheter. It is not uncommon for urinary tract infections to be observed within a few days.
Consequently, the patent literature is replete with reference to the art of coating such catheters, e.g. silicone rubber catheters, with various microbiocides, antibiotics or other bioactive reagents in order to ward off infections caused by invading organisms. By way illustration, mention may be made of U.S. Pat. Nos. 4,318,947 issued to Joung; 4,479,795 of Mustacich et. al.; 4,515,593 of Norton; and 4,539,234 of Sakamoto et. al., as well as the patents cited in this patents.
While in its broadest sense, the present invention is also directed to the art of coating catheters to present adverse reactions, particularly infection, induced by their use, the task of invention and, consequently, its solution are vastly different.
While much attention has been focused on coating catheters with a microbiocide or the like in order to bar the avenue for entry of pathogenic organisms, the present invention is instead concerned with an entirely different source of danger, namely infection or other injury which can result from the abrasive nature of the catheter when inserted in the body cavity, specifically those catheters made from silicone rubber.
Of particular concern are urinary tract infections resulting from the use of silicone rubber urethral catheters such as a Foley catheter. While the present invention is not so restricted, it will accordingly be discussed hereinafter, for purposes of illustration, by reference thereto.
In general silicone rubber catheters may be characterized as having a surface which feels somewhat rough and having an undesirably high coefficient of friction. This friction can induce abrasion to the delicate cavity walls, e.g. mucosa or endothelia linings, into which it is inserted and the abrasive action can in turn provide a source of infection.
The task of the invention may accordingly be said to improve the surface morphology so as to provide a smooth, lubricious surface which will appreciably lower the coefficient of friction and greatly facilitate insertion minimizing if not totally preventing harmful abrasion.